A coalition of British MEPs warned that the draft law could weaken quality standards by forcing countries with strict rules, such as the UK, to accept products that are tested under less rigorous systems elsewhere.

But the Finnish commissioner insisted there was “no indication” that the proposal would undermine the quality of hallmarking systems.

“The purpose of this proposal is not to reduce protection but to allow free movement of these articles on the basis of conformity assessment procedures – ensuring a high level of consumer protection,” he said.

The proposal, first launched in 1993, has been retabled by the Italian presidency after being shelved for 20 years.

Rome is under pressure from its huge jewellery industry that believes the law would boost access to big export markets.

Liberal Democrat MEP Nick Clegg told European Voice: “The concern is very simple. If you live in the UK and a number of other countries, there are very long-established methods by which the quality of jewellery is stamped. But some countries, such as Germany, had no quality guarantee at all.”

At the same time, claimed Clegg, a separate international accord already allows for mutual recognition of quality standards between recognised assay offices. The EU law, he said, would risk “reinventing the wheel”.

“I am not theologically opposed and have no axe to grind. It is just that the case has not been made for the directive. I am not surprised it has languished since the 1990s,” added Clegg, who will soon stand for election as a member of the British parliament for the city of Sheffield, home to one of the UK’s four assay offices.